The present invention relates to a gas generating apparatus which generates gases for inflating and expanding an airbag. More particularly, the present invention is concerned with a gas generating apparatus of the type in which a filter chamber and a combustion chamber are separated from each other.
Conventional gas generating apparatuses are broadly sorted into two types: a single-chamber type in which a propellant and a filter are accommodated in a common chamber as disclosed, for example, in WO 99/08907 (which is incorporated herein by reference in its entirety), and a separate-chamber type in which a propellant and a filter are disposed in separate chambers as disclosed in, for example, DE 298 19 168 (which is incorporated herein by reference in its entirety). In the gas generating apparatus of the separate-chamber type, a combustion chamber accommodating a propellant and a filter chamber accommodating a filter are separated from each other by a bulkhead or a partition in which a communication hole is formed. This communication hole maintains communication between the combustion chamber and the filter chamber until the maximum combustion pressure is reached after the start of the combustion. Thus, the escape of the combustion gas into the filter chamber starts right after the start of the combustion; the inflow of gas causes a little delay to rise the combustion pressure to the maximum. This delay slows the speed of the combustion.
U.S. Pat. No. 6,032,979 (which is incorporated herein by reference in its entirety) discloses a gas generating apparatus (referred to also as an xe2x80x9cinflatorxe2x80x9d, hereinafter) having first and second chambers, wherein an outlet orifice of the second chamber is in fluid communication with the content of the first chamber.
These are representative examples of the shortcomings in the prior art. Accordingly, there is a need to improve the initial restraining capability to be provided by an airbag by shortening the starting timing of rising the inner pressure by shortening the period required from the start of rising the inner pressure until the inner pressure reaches the maximum value.
There also is a demand for an inflator which affords a greater degree of design freedom in regard to the positions of gas-discharging ports.
An inflator is also demanded which affords a greater degree of design freedom in regard to the shape so as to be adaptable to a variety of installation positions.
It is also desirable that an inflator has a high efficiency of cooling the combustion gas.
According to the present invention a gas generating apparatus is provided. The apparatus includes a first combustion chamber having a first opening and a second combustion chamber having a second opening. Each of the combustion chambers contains an ignitor and a propellant. The apparatus includes a filter chamber accommodating a filter, wherein said filter chamber is separated from each said combustion chambers. The apparatus is configured so that a combustion gas produced in the first combustion chamber exits the first combustion chamber through the first opening and enters a first portion of the filter chamber without passing through the second chamber. The apparatus includes a reverse-flow prevention member provided in the second opening thereby preventing the combustion gas generated in the first combustion chamber from flowing into the second combustion chamber.
The apparatus is configured so that a combustion gas produced in the second combustion chamber exits the second combustion chamber through the second opening and enters a second portion of the filter chamber without passing through the first combustion chamber. The second combustion chamber may include a third opening positioned to allow the combustion gas produced in the second combustion chamber to exit the second combustion chamber and enter the filter chamber without passing through the first combustion chamber. Furthermore, the first and second openings may be spaced apart so that the combustion gases exiting from the first and second combustion chambers substantially permeate different regions of the filter.
The apparatus may further include a separating member positioned to separate the first and second combustion chambers from the filter chamber. The separating member may contain the first and second openings. The apparatus may include a first closure device blocking the first opening and being configured to open when the pressure in the first combustion chamber reaches a first predetermined value; and a second closure device blocking the second opening being configured to open when the pressure in the second combustion chamber reaches a second predetermined value.
In an alternative embodiment of the present invention, a gas generating apparatus comprising a first combustion chamber including a first opening and a second combustion chamber including a second opening is provided. The apparatus may further include a filter chamber accommodating a filter, wherein said filter chamber is separated from each said combustion chambers. The apparatus may be configured so that a first combustion gas produced in the first combustion chamber exits the first combustion chamber through the first opening and enters a first portion of the filter chamber without passing through the second chamber and a second combustion gas produced in the second combustion chamber exits the second combustion chamber through the second opening and enters a second portion of the filter chamber without passing through the first combustion chamber. The first and second portions of the filter chamber are located apart so that the combustion gases exiting from the first and second combustion chambers substantially permeate different regions of the filter.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed.